<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>css书写方式权重判断</title>
   <!-- <link rel="stylesheet" href="../css/demo03.css">-->
    <style>
        /*
          id >  class
        */
        /*.one {
            height: 300px;
            width: 300px;
            background-color: yellowgreen;
        }
        #one {
            background-color: yellowgreen;
        }*/
        /*并集*/
        #one,.one{
            height: 200px;
            width: 200px;
            background-color: yellowgreen;
            border: 1px solid red;
        }

        /*交集*/
        #one.one{
            border-radius: 20px;
        }

    </style>
</head>
<body>

    <div id="one" class="one"></div>
    <div class="one"></div>

</body>
</html>